Radio waves detected from Earth-like exoplanet betray its magnetic field

New Delhi: Researchers have identified an Earth-like exoplanet, a rocky one orbiting a star about 12 light years from Earth, that could have a magnetic field like Earth does.

In addition to pointing compass needles in the north direction, Earth's magnetic field helps preserve its atmosphere by deflecting high energy particles and plasma regularly blasted out of the sun, thereby, helping sustain life on the planet.

Therefore, the possible existence of a magnetic field on an exoplanet, called YZ Ceti b, could potentially signal habitability of life on that planet, the researchers said.

Astronomers Sebastian Pineda and Jackie Villadsen from University of Colorado (US) and Bucknell University (US), respectively, observed a repeating radio signal emanating from the star YZ Ceti, using the Karl G. Jansky Very Large Array, a radio telescope operated by the US National Science Foundation's National Radio Astronomy Observatory.

Their findings are published in the journal Nature Astronomy.

"Whether a planet survives with an atmosphere or not can depend on whether the planet has a strong magnetic field or not," explained Pineda.

Villadsen first isolated the radio signal while pouring over data at her home on a weekend.

"We saw the initial burst and it looked beautiful," said Pineda. "When we saw it again, it was very indicative that, OK, maybe we really have something here." The astronomers theorised that the interactions between the magnetic field of the planet and the star it orbits were giving rise to the stellar radio waves that they detected. However, they said, that for such waves to be detected over long distances, they would have to be very strong.

They further said that they were looking for a method to see these invisible magnetic fields of such distant, tiny Earth-sized planets. Previously, magnetic fields have been detected on massive Jupiter-sized exoplanets.

"If the planet has a magnetic field and it plows through enough star stuff, it will cause the star to emit bright radio waves," they concluded.

The small red dwarf star YZ Ceti and its known exoplanet, YZ Ceti b, provided an ideal pair, said the scientists, because the exoplanet, being very close to the star, orbits it in just two days. The smallest orbit in our solar system, that of Mercury, is 88 days long.

As plasma from YZ Ceti careens off the planet's magnetic "plow," it then interacts with the magnetic field of the star itself, which generates radio waves strong enough to be observed on Earth.

The strength of the planet's magnetic field can then be measured by measuring that of the radio waves thus emitted.

"The search for potentially habitable or life-bearing worlds in other solar systems depends in part on being able to determine if rocky, Earth-like exoplanets actually have magnetic fields," says National Science Foundation's (NSF's) Joe Pesce, program director for the National Radio Astronomy Observatory.

"This research shows not only that this particular rocky exoplanet likely has a magnetic field but provides a promising method to find more."